Question

我试图在NHibernate中复制这个SQL查询：

SELECT player.NAME, 
       Sum(achievement.value) AS 'Goals Scored' 
FROM   player 
       JOIN playerperformance 
         ON playerperformance.player_id = player.id 
       JOIN achievement 
         ON achievement.playerperformance_id = playerperformance.id 
WHERE  achievement.descriptor = 'Goals Scored' 
GROUP  BY player.NAME, 
          player.id 
ORDER  BY 'Goals Scored' DESC

这是我的NHibernate LINQ查询：

_dataAccessor.QueryOver<Player>()
    .Inner.JoinQueryOver<PlayerPerformance>(player => player.Performances)
    .Inner.JoinQueryOver<Achievement>(perf => perf.Achievements, () => achievementAlias)
    .Where(a => a.Descriptor == "Goals Scored")
    .SelectList(list => list.SelectGroup(player => player.Id).SelectSum(() => achievementAlias.Value))
    .OrderBy(a => a.Value).Desc
    .List()
    ;

这几乎是正确的。但OrderBy出错了。我不知道在OrderBy lambda中放什么会使它在SelectSum(...)部分的别名上排序。生成的SQL中有一个别名：

SELECT this_.id                AS y0_, 
       Sum(achievemen2_.value) AS y1_ 
FROM   [player] this_ 
       INNER JOIN [playerperformance] playerperf1_ 
               ON this_.id = playerperf1_.player_id 
       INNER JOIN [achievement] achievemen2_ 
               ON playerperf1_.id = achievemen2_.playerperformance_id 
WHERE  achievemen2_.descriptor = @p0 
GROUP  BY this_.id 
ORDER  BY achievemen2_.value DESC

所以我需要做的就是说服NHibernate做ORDER BY y1_而不是ORDER BY achievemen2_.Value。但我无法弄清楚如何获得总和的别名。

有什么想法吗？

Answer 1

我明白了。 SelectSum(...)有WithAlias方法，因此我可以指向表示总和的整数别名。然后我只需使用OrderByAlias(...)而不是OrderBy(...)：

int sumAlias = 0;

_dataAccessor.QueryOver<Player>()
    .Inner.JoinQueryOver<PlayerPerformance>(player => player.Performances)
    .Inner.JoinQueryOver<Achievement>(perf => perf.Achievements, () => achievementAlias)
    .Where(a => a.Descriptor == "Goals Scored")
    .SelectList(list => list.SelectGroup(player => player.Id).SelectSum(() => achievementAlias.Value).WithAlias(() => sumAlias)
    .OrderByAlias(() => sumAlias).Desc
    .List<object[]>()
    ;

获取SelectSum的别名

1 个答案: